So far, Hotmelt Asphalt waterproofing methods have often been used for the purpose of making structures for engineering works and buildings waterproof. However, these methods have involved many problems such as foul odors and fuming, a possibility of catching fire, and a risk of causing workers to have burns, because asphalt is melted by heat for use on site.
In recent years, these methods have been superseded by normal temperature waterproofing methods using a rubber modified asphalt emulsion. One typical method involves spraying a mixture of a rubber modified asphalt emulsion and a gelatinizing agent onto an application surface to form thereon a rubber modified asphalt layer, and another method comprises injecting a rubber modified asphalt emulsion and a coagulating agent through separate nozzles onto an application surface while they are brought into contact mixing with each other in the air, thereby forming a rubber modified asphalt layer on the application surf ace.
For instance, reference is made to JP-B 56-48652 and 58-41107. According to the former, a flow of an asphalt latex mixture consisting of asphalt or its mixture with oil and latex, and a flow of mixed emulsion consisting of an aqueous emulsion made up of at least one of asphalt, oil and latex and a gelatinizing agent are sprayed onto an application surface while they are continuously mixed together, thereby forming thereon a rubber modified asphalt layer according to the latter, an anionic rubber modified asphalt emulsion having a total solid content exceeding 70% by weight (usually 80 to 85% by weight) and a polyvalent metal salt (in the form of a 1-15% by weight aqueous solution) that is a gelatinizing agent are injected through separate airless type spraying machines onto an application surface while they are brought into contact mixing with each other in the air, thereby forming a rubber modified asphalt layer on the application surface.
Another normal temperature waterproofing method, now available, is of the self-hardening type wherein a hydraulic inorganic material such as cement is used to coagulate a rubber modified asphalt emulsion. This method makes use of the hydration reaction of the hydraulic inorganic material with water present in the rubber modified asphalt emulsion to remove that water as crystal water, thereby forming a rubber modified asphalt layer. The hydraulic inorganic material known to coagulate the rubber modified asphalt emulsion, for instance, is portland cement that may be used alone or in combination with alumina cement, etc.
However, the normal temperature waterproofing method disclosed in JP-B 56-48652 is now found to be quite unpractical, because it, when applied to an upright or slope surface, is likely to cause sagging due to relatively long time for coagulate. The normal temperature waterproofing method set forth in JP-B 58-41107, i.e., that of the airless spray type wherein the emulsion is instantaneously coagulated by the co-spraying of a coagulating agent is advantageous in that the exuding amount of water separated by the coagulation of the spraying material is so limited that some considetrable improvement is made in the blistering of the formed rubber modified asphalt layer. A problem with this method, however, is that the rubber modified asphalt layer tends to peel off the application surface, if it remains wet, due to the water exuding from the rubber modified asphalt emulsion. Another problem arises due to the fact that the polyvalent metal salt used as the coagulating agent is mainly calcium chloride; that is, the surface of reinforced concrete to which the method has been applied is apt to suffer an attack by salt and rust.
The normal temperature waterproofing method making use of a hydraulic inorganic material such as cement to coagulate a rubber modified asphalt emulsion, when applied to ceilings or walls, has some practical difficulty, because the resulting rubber modified asphalt layer coagulate so slowly that it does not become hard enough within a short time.
Thus, there is a strong demand for the development of a rubber modified asphalt type of waterproofing composition which are free from all the problems of the normal temperature waterproofing methods above mentioned.